Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
import queue
INF = 1 << 30
H , W= map(int, input().split())
que = [(0, 0)]
S = [input() for i in range(H)]
flag = [[INF for i in range(W)] for j in range(H)]
flag[0][0] = 1
cnt = sum(row.count('.') for row in S)
while que:
	y, x = que[0]
	que.pop(0)
	for ny, nx in [1, 0], [-1, 0], [0, 1], [0, -1]:
		nx += x
		ny += y
		if ny >= 0 and nx >= 0 and ny < H and nx < W and S[ny][nx] != '#' and flag[ny][nx] > flag[y][x] + 1:
			que.append((ny, nx))
			flag[ny][nx] = flag[y][x] + 1
			if (ny, nx) == (H - 1, W - 1):
				print(cnt - flag[ny][nx])
				exit()
print(-1)